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https://xkcd.com

Performance

· 17 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
92
GRADE
A
FIX
1
REVIEW
2
PASS
12
INFO
2

Performance-focused optimization plan with CWV assessment, top offenders, and time estimates

Mobile Desktop
70
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
76
Accessibility Measures how accessible the page is for users with disabilities. Checks color contrast, ARIA labels, and semantic HTML.
96
Best Practices Checks for modern web development best practices including HTTPS, no console errors, and secure JavaScript.
92
SEO Measures basic SEO optimizations: meta tags, crawlability, link text, and mobile friendliness.

First Contentful Paint First Contentful Paint — how long until the browser renders the first piece of content. Under 1.8s is good.

904 ms

Largest Contentful Paint Largest Contentful Paint — how long until the largest visible element loads. Under 2.5s is good.

4.80 s

Total Blocking Time Total Blocking Time — total time the main thread was blocked, preventing user input. Under 200ms is good.

0 ms

Cumulative Layout Shift Cumulative Layout Shift — measures visual stability. How much the page layout shifts during loading. Under 0.1 is good.

0.250

Speed Index Speed Index — how quickly content is visually displayed during load. Under 3.4s is good.

904 ms

Time to Interactive Time to Interactive — how long until the page is fully interactive and responds to user input. Under 3.8s is good.

4.80 s

Page Load Progression

375 ms
750 ms
1.1 s
1.5 s
1.9 s
2.2 s
2.6 s
3.0 s
Checks
17
12 PASS 2 REVIEW 1 FIX
D
Third-Party Impact
Action
97% third-party, 0 ms blocking
FIX
97% third-party, 0 ms blocking
Warning::
Third-party code accounts for 97% of page weight (622.4 KiB of 639.1 KiB)
Info::
Third-party blocking time is low (0 ms)
97%
First-party Third-party
B
Image Optimization
4 images, 0 KB saveable
REVIEW
4 images, 0 KB saveable
Warning::
https://imgs.xkcd.com/comics/types_of_board_game_2... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
4 images 634 KB
0 oversized -0 KB
4 legacy format
1 missing dimensions CLS risk

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

C
Green Hosting
Action
Whether the site is served from green-energy infrastructure
REVIEW

Green Hosting

No green hosting detected

A+
Page Weight Budget
639 KB transferred, 7 requests
PASS
639 KB transferred, 7 requests
Info::
Page weighs 644 KB (639 KB transferred)
Info::
7 HTTP requests
Info::
Estimated 0.13 g CO2 per page load
639 KB / 2.4 MB budget
639 KB transferred
7 requests
0.13 g CO2 per page load
Images 633.5 KiB 99%
HTML 2.7 KiB 0%
CSS 1.6 KiB 0%
Other 1.2 KiB 0%
0 2.4 MB 4.9 MB
Under budget
A+
Text Compression
All text resources are compressed
PASS
All text resources are compressed
Info::
All text resources are compressed
All text resources are properly compressed.
A+
JS Execution Cost
239ms total JS execution
PASS
239ms total JS execution
Info::
https://xkcd.com/: 124ms CPU time
Info::
Unattributable: 115ms CPU time
Info::
Third-party scripts: 115ms (48% of total)

Main Thread Breakdown

Other 49% Style & Layout 35% Script Evaluation 8% Rendering 4%
ScriptTotalScriptingParse/CompileParty
https://xkcd.com/124ms4ms1ms1st
Unattributable115ms13ms0ms3rd
A+
Font Loading
No web fonts (system fonts)
PASS
No web fonts (system fonts)
Info::
No web fonts loaded — system fonts are fastest
No web fonts loaded — system fonts are optimal.
A+
JS Bundles
No JavaScript
PASS
No JavaScript
Info::
No JavaScript bundles
No JavaScript files loaded.
A+
Resource Caching
All resources properly cached
PASS
All resources properly cached
Info::
No caching issues found
All static resources have appropriate caching headers.
A+
Critical Rendering Path
No render-blocking resources
PASS
No render-blocking resources
Info::
No render-blocking resources detected
A+
Resource Hints
No optimization needed
PASS
No optimization needed
Info::
No resource hint issues
A
Page Weight Inventory
7 resources · 639 KB · 0 KB savings available
PASS
7 resources · 639 KB · 0 KB savings available
Info::
Within 1MB page-weight target
Got: 639 KB
Warning::
3 third-party resources (97% of weight)
Info::
1 resources over 200KB
7 resources · 639.1 KiB · 3 third-party Within 1MB page-weight target
Image 99% · 634.7 KiB
Document 0% · 2.7 KiB
CSS 0% · 1.6 KiB
A+
Render-Blocking Resources
No render-blocking resources detected
PASS
No render-blocking resources detected
Info::
No render-blocking resources detected in <head>
A+
Third-Party Resources
No third-party resources detected
PASS
No third-party resources detected
A+
HTTP Caching
max-age=300 (5 minutes)
PASS
max-age=300 (5 minutes)
Info::
Cache-Control header is set
Got: max-age=300
Info::
Effective TTL: 5 minutes (max-age=300)
Info::
ETag present — enables conditional (304) responses
Cache-Control

max-age=300

DirectiveValueMeaning
max-age300Cache for 5 minutes
Effective TTL: 300 seconds
Network Waterfall
7 requests over 84ms
INFO
0 ms 1.0 s 2.0 s 3.0 s 4.0 s 5.0 s FCP 904 ms LCP 4.8 shttps://xkcd.com// https://xkcd.com/ — 200 — 2.7 KiB — 10 ms — http/1.1https://xkcd.com/s/7d94e0.css/s/7d94e0.css https://xkcd.com/s/7d94e0.css — 200 — 1.6 KiB — 5 ms — http/1.1https://xkcd.com/s/0b7742.png/s/0b7742.png https://xkcd.com/s/0b7742.png — 200 — 11.2 KiB — 7 ms — http/1.1https://imgs.xkcd.com/comics/types_of_board_game_2x.pngimgs.xkcd.com/comics/types_of_board... https://imgs.xkcd.com/comics/types_of_board_game_2x.png — 200 — 573.6 KiB — 45 ms — http/1.1https://imgs.xkcd.com/s/a899e84.jpgimgs.xkcd.com/s/a899e84.jpg https://imgs.xkcd.com/s/a899e84.jpg — 200 — 21.3 KiB — 23 ms — http/1.1https://imgs.xkcd.com/s/temperature.pngimgs.xkcd.com/s/temperature.png https://imgs.xkcd.com/s/temperature.png — 200 — 27.4 KiB — 22 ms — http/1.1https://xkcd.com/s/919f27.ico/s/919f27.ico https://xkcd.com/s/919f27.ico — 200 — 1.2 KiB — 3 ms — http/1.1
HTML JavaScript CSS Images Fonts XHR/Fetch Other
Third-Party Script Cost
Per-script blocking time, transfer cost, and cache headers
INFO
48% of JavaScript execution is third-party
First-party Third-party 115ms · 0KB · $2/mo
Unattributable
Other
Optional
Execution 115ms
Transfer 0 KB
Monthly Cost $2/mo

48% of JavaScript execution time comes from third-party scripts.

Why this matters

Third-party scripts (analytics, ads, social, A/B testing) often dominate execution time — every one is a perf-and-privacy tax.

Learn more ▾

Each third-party script is a black box: you don't control when it loads, what it executes, or how much it grows. They often account for a major share of total blocking time on average sites (HTTP Archive's Web Almanac documents the trend). Audit which ones you actually need, defer the rest, and use facade patterns (lite-youtube, lite-vimeo) for embedded media.

Source: web.dev / HTTP Archive Web Almanac

How third-party costs are calculated

All checks on this page are automated. Results are estimates - run targeted manual reviews when the score affects a release decision.

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